Spring Boot中CompletableFuture调用API触发请求上下文异常排查

我尝试使用CompletableFuture同时发起多个API调用以减少用户等待时间，代码如下：

@Async
public CompletableFuture<CommonDataDTO> commonData() throws JsonProcessingException, ExecutionException, InterruptedException {
    CompletableFuture<UserDTO[]> completableFutureUser = CompletableFuture.supplyAsync(() -> {
        try {
            return  apiHelper.getEmployee();
        } catch (JsonProcessingException e) {
            return new UserDTO[0];
        }
    });
    CompletableFuture<ContactDTO[]> completableFutureContact = CompletableFuture.supplyAsync(() -> {
        try {
            return  apiHelper.getTravelAgent();
        } catch (JsonProcessingException e) {
            return new ContactDTO[0];
        }
    });
    CompletableFuture<CurrencyRateDTO[]> completableFutureCurrency = CompletableFuture.supplyAsync(() -> apiHelper.getCurrencyRate("site"));

    return CompletableFuture.allOf(completableFutureUser, completableFutureContact, completableFutureCurrency).thenApply(v -> {
        return new CommonDataDTO(Arrays.stream(completableFutureUser.join()).toList(), Arrays.stream(completableFutureContact.join()).toList(), Arrays.stream(completableFutureCurrency.join()).toList());
    });
}

运行代码时出现如下错误：

java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.

我已在Application类添加了@EnableAsync注解，也曾尝试将allOf替换为thenCombine，但问题依旧。请问我哪里操作有误？

核心原因 #

1. CompletableFuture.supplyAsync()默认使用ForkJoinPool.commonPool()，该线程池的线程不属于Spring请求线程上下文，而apiHelper的内部方法大概率依赖了请求上下文信息（比如RequestAttributes、Session、请求头参数等），导致异步线程无法获取绑定的请求对象，触发异常。
2. 方法上标注的@Async与内部手动创建的CompletableFuture形成双重异步，进一步脱离了请求上下文。

解决步骤 #

• 移除方法上的@Async注解
  你已经通过CompletableFuture实现了并行异步调用，@Async会让整个方法在额外的异步线程执行，叠加后更容易引发上下文丢失问题，因此需要移除该注解。

• 配置异步线程继承请求上下文
  如果apiHelper的方法必须依赖请求上下文，需自定义Spring异步线程池并配置任务装饰器传递上下文：

  @Configuration
  @EnableAsync
  public class AsyncConfig implements AsyncConfigurer {
      @Override
      public Executor getAsyncExecutor() {
          ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
          executor.setCorePoolSize(4);
          executor.setMaxPoolSize(10);
          executor.setQueueCapacity(20);
          executor.setThreadNamePrefix("Async-");
          // 任务装饰器：传递请求上下文到异步线程
          executor.setTaskDecorator(runnable -> {
              RequestAttributes attributes = RequestContextHolder.getRequestAttributes();
              return () -> {
                  try {
                      RequestContextHolder.setRequestAttributes(attributes);
                      runnable.run();
                  } finally {
                      RequestContextHolder.resetRequestAttributes();
                  }
              };
          });
          executor.initialize();
          return executor;
      }
  }
  

  之后在supplyAsync中指定该自定义线程池：

  @Autowired
  private Executor asyncExecutor;
  
  // 使用自定义线程池执行异步任务
  CompletableFuture<UserDTO[]> completableFutureUser = CompletableFuture.supplyAsync(() -> {
      try {
          return apiHelper.getEmployee();
      } catch (JsonProcessingException e) {
          return new UserDTO[0];
      }
  }, asyncExecutor);
  

• 避免异步线程依赖请求上下文（推荐）
  尽量在主线程中提前取出请求上下文里的必要参数，直接传递给apiHelper的方法，而非让apiHelper在异步线程中获取上下文：

  // 主线程中获取请求参数
  String site = request.getParameter("site");
  // 传递参数到异步任务
  CompletableFuture<CurrencyRateDTO[]> completableFutureCurrency = CompletableFuture.supplyAsync(() -> apiHelper.getCurrencyRate(site), asyncExecutor);
  

内容的提问来源于stack exchange，提问作者Nguyen Andrew